Vehicles having a disconnecting driveline are increasingly common in modern vehicles. Disconnecting all-wheel drive drivelines, for example, provide all-wheel drive capabilities in some situations where additional traction needed, but may be disconnected to permit the driveline to be operated in a two-wheel drive mode for increased fuel economy. Disconnecting all-wheel drive drivelines typically include a primary axle, which is typically the front axle, a secondary axle, and a power take-off unit, which that can transmit power between the primary and secondary axle, a first disconnect clutch, which can selectively interrupt power transmission between the power take-off unit and the secondary axle, and one or more second disconnect clutches, which can selectively interrupt power transmission between the secondary axle and one or more of the vehicle wheels that are driven by the secondary axle.
Certain disconnecting driveline configurations, such as those having a secondary axle that selectively disconnects one wheel from one of the outputs of a differential assembly in the secondary axle, provide a torque transmission path between the non-disconnected wheel and the differential assembly that permits the gearing within the differential assembly to be “back driven” when the secondary axle is operated in the disconnected mode. Such configurations do not maximize the fuel efficiency that could be obtained through the disconnection of the secondary axle.
Other disconnecting driveline configurations that disconnect both of the wheels from the outputs of the differential assembly in the secondary axle, via multiple clutches or couplings, for example, are not entirely satisfactory in that they require multiple actuators and/or take up too much space. Consequently, there remains a need in the art for a disconnecting driveline having an improved disconnectable secondary axle in which both of the wheels driven by secondary axle can be disconnected from the differential assembly of the secondary axle.